Probably 90% of port jobs are automated away compared to 50 years ago.

Yes. For an extreme example, here's Rotterdam's container port. Zero people in the quay area.[1] This is sped up, but entirely real. Not only are the vehicles driverless, so are the cranes. A few people in a control tower oversee that operation.

[1] https://www.youtube.com/watch?v=zm_rlLyelQo

Amazing

Containerization alone is probably responsible for half of that.

If you want a good read on containerization, I'd really recommend reading 'The Box', a history of shipping containers. For a topic that might sound bland, it's fascinating.

https://www.amazon.com/Box-Shipping-Container-Smaller-Econom...

Also, the ship's crew are doing most maintenance underway, which keeps the asset producing value. Pretty much the only maintenance done on cargo ships at a port is stuff that requires a drydock. It's actually cheaper overall to have the maintenance crew ride the ship around the world (and also do the small number of sailing tasks that would be expensive to automate) than it is to take the ship out of service at ports to, say, repaint everything, or change the engine oil.

Rolls-Royce would disagree https://gcaptain.com/rolls-royce-launches-strategic-partners...

The world's largest container ships run with a crew of about seven people.

Do you have a source for that? I once asked a captain of a 14.000+ TEU vessel if they really only needed the minimum amount of crew. According to him theory and practice are vastly different. Meaning: a news article explaining that a vessel can be run with X amount of people doesn't mean there are only X amount of people on board.

Secondly, there's all kinds of regulations. A container vessel is operated 24/7. If 7 is the amount of people working on it at a time, in practice the crew will be twice that.

In any case, your response lacks a lot. The person you replied to talked about big boat shipping and how it is not going to be automated any time soon. You only account for the crew on a vessel. There's the customers (loads of which still like to send a fax), lots of outdated governments, outdated vendors, other companies, etc.

You're right, 'can be run' != 'is run'. According to Wikipedia, the Emma Maersk has a crew of 13:

https://en.wikipedia.org/wiki/Emma_M%C3%A6rsk

Still not a lot of fat to cut for a ship with the capacity of a medium size port.

The captains I asked was a captain for one of Maersk E-class vessels. They don't use the minimal amount. Unfortunately it's been a few years since I asked and I don't remember much of the details, just that the stated minimal crew is not what's on a vessel.

If a ship has no people, it also needs no bridge, control room, bedrooms, kitchen etc. If it has none of that, it needs to water system, toilets, lighting, heating etc.

And with all that gone, you could fit a lot more cargo on the same size boat.

Can you express "a lot" as a percentage of existing capacity? Because it seems like, relative to the amount of cargo space these ships already have, that percentage would be pretty small.

By eyeballing an Emma Maersk diagram, I think you could get three more stacks of containers, for ~5% more capacity.

Related question: if they wanted 5% more capacity in the Emma Maersk, what kept them from just building it that way? Are the sizes of these ships a fuel and utilization efficiency optimization problem?

That's true that newer ships have more automation so crew size reduced dramatically. For example there is no man in machine rooms any more in new ships.

Another thing, crew size would be 3x of needed crew for one shift because in ships there are three shifts, one shift lasts in 8 hours.

(Source: I am originally Naval Architect)

They could be electric by generating their own power, with a nuclear reactor for instance.

Most people would call those "nuclear". I'm sure you'd find some if you googled them.